Method and structure for receiving a micro device

ABSTRACT

A method and structure for receiving a micro device on a receiving substrate are disclosed. A micro device such as a micro LED device is punched-through a passivation layer covering a conductive layer on the receiving substrate, and the passivation layer is hardened. In an embodiment the micro LED device is punched-through a B-staged thermoset material. In an embodiment the micro LED device is punched-through a thermoplastic material.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/008,372, filed Jan. 27, 2016, which is a continuation of U.S. patentapplication Ser. No. 14/563,763, filed Dec. 8, 2014, now U.S. Pat. No.9,263,627, which is a divisional application of U.S. patent applicationSer. No. 13/562,184 filed Jul. 30, 2012, now U.S. Pat. No. 8,933,433,which is incorporated herein by reference.

BACKGROUND

Field

The present invention relates to micro devices. More particularlyembodiments of the present invention relate to a method and structurefor receiving a micro device on a receiving substrate.

Background Information

Integration and packaging issues are one of the main obstacles for thecommercialization of micro devices such as radio frequency (RF)microelectromechanical systems (MEMS) microswitches, light-emittingdiode (LED) display and lighting systems, MEMS, or quartz-basedoscillators.

Traditional technologies for transferring of devices include transfer bywafer bonding from a transfer wafer to a receiving wafer. One suchimplementation is “direct printing” involving one bonding step of anarray of devices from a transfer wafer to a receiving wafer, followed byremoval of the transfer wafer. Another such implementation is “transferprinting” involving two bonding/de-bonding steps. In transfer printing atransfer wafer may pick up an array of devices from a donor wafer, andthen bond the array of devices to a receiving wafer, followed by removalof the transfer wafer. Some printing process variations have beendeveloped where a device can be selectively bonded and de-bonded duringthe transfer process. In both traditional and variations of the directprinting and transfer printing technologies, the transfer wafer isde-bonded from a device after bonding the device to the receiving wafer.In addition, the entire transfer wafer with the array of devices isinvolved in the transfer process.

Other technologies for transferring of devices include transfer printingwith elastomeric stamps. In one such implementation an array ofelastomeric stamps with posts matching the pitch of devices on a sourcewafer are brought into intimate contact with the surface of the deviceson the source wafer and bonded with van der Walls interaction. The arrayof devices can then be picked up from the source wafer, transferred to areceiving substrate, and released onto the receiving substrate.

SUMMARY OF THE INVENTION

A method and structure for receiving a micro device on a receivingsubstrate are described. In an embodiment, a structure includes asubstrate, a conductive layer on the substrate, and a micro LED deviceon the conductive layer. The micro LED device includes a micro p-ndiode, a metallization stack between the micro p-n diode and theconductive layer, and a quantum well layer within the micro p-n diode. Abonding layer may optionally be formed between the metallization stackand the conductive layer. For example, the bonding layer can be amaterial such as indium, gold, silver, molybdenum, tin, aluminum,silicon, and alloys thereof. A thermoplastic or thermoset passivationlayer laterally surrounds the quantum well layer of the micro LEDdevice. A second conductive layer is formed on a top surface of themicro LED device. For example, the two conductive layers can beelectrodes such as anode or cathode, or anode or cathode lines. Abarrier layer can be formed on the second conductive layer, and a covercan be formed over the micro LED device. The cover may be conformal to atopography of the micro LED device or be a rigid cover plate. A blackmatrix material can be formed around the micro LED device and underneaththe cover.

In an embodiment, the receiving substrate is a lighting or displaysubstrate, and the structure can be configured to emit light from a topsurface, through the substrate and a bottom surface, or both. In anembodiment, the passivation layer is transparent in the visiblewavelength range, e.g. 380 nm-750 nm. For example, benzocyclobutene(BCB) and epoxy are suitable transparent thermoset materials. The firstand/or second conductive layer may also be formed of a transparentmaterial such as indium-tin-oxide (ITO) andpoly(3,4-ethylenedioxythiophene (PEDOT). The conductive layer(s) canalso include nanoparticles such as silver, gold, ITO andindium-zinc-oxide (IZO). In an embodiment, one of the conductive layersis reflective to the visible wavelength range. For example, the secondconductive layer may be reflective for a bottom emitting structure.Alternatively, or in addition, a layer reflective to the visiblewavelength range can be formed over the micro LED device for a bottomemitting structure.

In an embodiment, the micro LED device is integrated into a pixel of adisplay substrate. For example, the micro LED device can be integratedinto a subpixel of the pixel, where the conductive layer and secondconductive layer are the anode and cathode, or vice-versa. A cover canbe formed over the subpixel with a black matrix material around themicro LED device in the subpixel, and underneath the cover. In anembodiment, the micro LED device emits a primarily blue, red, or greenlight. An arrangement of red, blue, and green micro LED devices may bearranged in separate subpixels of an RGB pixel. In an embodiment, themicro LED device is integrated into an active matrix pixel display inwhich each subpixel includes working circuitry such as a switchingtransistor, driving transistor, and storage capacitor. For example, theswitching and driving transistors can be thin film transistors. In anembodiment, the micro LED device is integrated into a passive matrixpixel display.

In an embodiment, a method of transferring a micro device to a receivingsubstrate includes picking up a micro device from a carrier substratewith a transfer head and placing the micro device on a conductive layerformed on the receiving substrate by punching the micro device through apassivation layer covering the conductive layer. The micro device may bepicked up from the carrier substrate with a variety of manners,including applying a voltage to the transfer head to generate anelectrostatic pick up pressure on the micro device. The micro device isthen released from the transfer head and the passivation layer ishardened so that the hardened passivation layer laterally surrounds themicro device. A variety of micro devices can be transferred inaccordance with embodiments of the invention, such as, a diode, LED,transistor, integrated circuit (IC), or microelectromechanical system(MEMS). In an embodiment, the micro device is a micro LED deviceincluding a micro p-n diode, a metallization stack between the micro p-ndiode and the conductive layer, and a quantum well layer within themicro p-n diode where the hardened passivation layer laterally surroundsthe quantum well layer of the micro LED device.

In an embodiment, the micro device is punched through a B-stagedthermoset passivation layer which is then hardened by curing theB-staged thermoset passivation layer, for example by the application ofheat or ultraviolet (UV) energy. The B-staged thermoset passivationlayer may first be formed by directly applying the B-staged thermosetpassivation layer, or first applying an A-staged thermoset passivationlayer on the receiving substrate and covering the conductive layer,followed by partially curing the A-staged thermoset passivation layer toform the B-staged thermoset passivation layer. The B-staged thermosetpassivation layer may also be heated during punch-through, which mayallow the B-staged thermoset passivation layer to soften or flow to aidin the punch-through. In an embodiment, the micro device is punchedthrough a thermoplastic passivation layer heated above its glasstransition temperature, followed by cooling below its glass transitiontemperature to harden the thermoplastic passivation layer. For example,the thermoplastic passivation layer is heated to a temperature above theglass transition temperature but below the melting temperature of thethermoplastic passivation layer.

In an embodiment, a second conductive layer may be formed over the microdevice and passivation layer. For example, the second conductive layercan be formed by deposition and etching a material such asindium-tin-oxide (ITO) or indium-zinc-oxide (IZO). The second conductivelayer can also be formed by ink jet printing a material such aspoly(3,4-ethylenedioxythiophene) (PEDOT) or a material containingnanoparticles such as of silver, gold, ITO, and IZO nanoparticles. Abarrier layer can be formed over the second conductive layer to protectagainst oxygen and moisture absorption, for example. Suitable depositiontechniques include, but are not limited to, atomic layer deposition(ALD) and ion sputtering.

The A-staged thermoset passivation layer can be deposited using avariety of suitable techniques such as spin coating, screen printing,ink jet printing, dispending and spray coating, followed by theselective removal of a portion to expose an electrode line, for exampleby laser scribing or photolithography. Alternatively, a patternedA-staged thermoset passivation layer can be selectively applied so thatthe opening exposing the electrode line is included.

In an embodiment, placing the micro device on the conductive layerincludes placing the micro device on a bonding layer formed on theconductive layer. For example, the bonding layer may include a materialsuch as indium, gold, silver, molybdenum, tin, aluminum, silicon, andalloys thereof. The method may additionally include heating thestructure to diffuse the bonding layer into the metal stack, or heatingthe structure to diffuse the bonding into a second bonding layer formedon the metal stack. Heating can be from a backside of the receivingsubstrate or from the transfer head, for example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional side view illustration of a receivingsubstrate in accordance with an embodiment of the invention.

FIG. 1B is a cross-sectional side view illustration of a receivingsubstrate in accordance with an embodiment of the invention.

FIG. 2 is a cross-sectional side view illustration of a patternedpassivation layer on a receiving substrate in accordance with anembodiment of the invention.

FIGS. 3A-3C are cross-sectional side view illustrations of an array oftransfer heads picking up an array of micro LED devices from a carriersubstrate in accordance with an embodiment of the invention.

FIG. 3D is a cross-sectional side view illustration of a transfer headholding a micro LED device over a receiving substrate with a patternedpassivation layer in accordance with an embodiment of the invention.

FIG. 3E is a cross-sectional side view illustration of an array oftransfer heads holding an array micro LED devices over a receivingsubstrate with a patterned passivation layer in accordance with anembodiment of the invention.

FIG. 4A is a cross-sectional side view illustration of a micro LEDdevice punched through a passivation layer on a receiving substrate inaccordance with an embodiment of the invention.

FIG. 4B is a cross-sectional side view illustration of an array of microLED devices punched through a passivation layer on a receiving substratein accordance with an embodiment of the invention.

FIG. 5 is a cross-sectional side view illustration of a conductive layerand barrier layer formed over a micro LED device on a receivingsubstrate in accordance with an embodiment of the invention.

FIG. 6 is a cross-sectional side view illustration of a cathode lineformed directly over a micro LED device on a receiving substrate inaccordance with an embodiment of the invention.

FIG. 7 is a cross-sectional side view illustration of a cathode line ona receiving substrate in accordance with an embodiment of the invention.

FIG. 8 is a cross-sectional side view illustration of cover layer formedover a micro LED device on a receiving substrate in accordance with anembodiment of the invention.

FIG. 9 is a cross-sectional side view illustration of a reflective layerand cover layer formed over a micro LED device on a receiving substratein accordance with an embodiment of the invention.

FIG. 10 is a cross-sectional side view illustration of a black matrixlayer and cover layer formed over a micro LED device on a receivingsubstrate in accordance with an embodiment of the invention.

FIGS. 11-12 are cross-sectional side view illustrations of attaching acover plate over a micro LED device on a receiving substrate inaccordance with an embodiment of the invention.

FIGS. 13-14A are cross-sectional side view illustrations of attaching acover plate and black matrix over a micro LED device on a receivingsubstrate in accordance with an embodiment of the invention.

FIG. 14B is a cross-sectional side view illustration of a cover plateand black matrix over an array of micro LED devices on a receivingsubstrate in accordance with an embodiment of the invention.

FIGS. 15-17 are schematic illustrations of passive matrix displaylayouts in accordance with embodiments of the invention.

FIG. 18 is a circuit diagram of a passive matrix display in accordancewith an embodiment of the invention.

FIG. 19 is a schematic illustration of a subpixel in an active matrixdisplay in accordance with embodiments of the invention.

FIG. 20 is a circuit diagram of a subpixel in an active matrix displayin accordance with an embodiment of the invention.

FIG. 21 is a circuit diagram of an active matrix display in accordancewith an embodiment of the invention.

FIG. 22 is a schematic illustration of a display device in accordancewith an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention describe a method and structure forreceiving a micro device or an array of micro devices such as microlight emitting diode (LED) devices on a receiving substrate. Forexample, the receiving substrate may be, but is not limited to, adisplay substrate, a lighting substrate, a substrate with functionaldevices such as transistors or integrated circuits (ICs), or a substratewith metal redistribution lines. While embodiments of the presentinvention are described with specific regard to micro LED devicescomprising p-n diodes, it is to be appreciated that embodiments of theinvention are not so limited and that certain embodiments may also beapplicable to other micro semiconductor devices which are designed insuch a way so as to perform in a controlled fashion a predeterminedelectronic function (e.g. diode, transistor, integrated circuit) orphotonic function (LED, laser).

In various embodiments, description is made with reference to figures.However, certain embodiments may be practiced without one or more ofthese specific details, or in combination with other known methods andconfigurations. In the following description, numerous specific detailsare set forth, such as specific configurations, dimensions andprocesses, etc., in order to provide a thorough understanding of thepresent invention. In other instances, well-known semiconductorprocesses and manufacturing techniques have not been described inparticular detail in order to not unnecessarily obscure the presentinvention. Reference throughout this specification to “one embodiment,”“an embodiment” or the like means that a particular feature, structure,configuration, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention.Thus, the appearances of the phrase “in one embodiment,” “in anembodiment” or the like in various places throughout this specificationare not necessarily referring to the same embodiment of the invention.Furthermore, the particular features, structures, configurations, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

The terms “spanning,” “over,” “to,” “between” and “on” as used hereinmay refer to a relative position of one layer with respect to otherlayers. One layer “spanning,” “over” or “on” another layer or bonded“to” another layer may be directly in contact with the other layer ormay have one or more intervening layers. One layer “between” layers maybe directly in contact with the layers or may have one or moreintervening layers.

The terms “micro” device, “micro” p-n diode or “micro” LED device asused herein may refer to the descriptive size of certain devices orstructures in accordance with embodiments of the invention. As usedherein, the terms “micro” devices or structures are meant to refer tothe scale of 1 to 100 μm. However, it is to be appreciated thatembodiments of the present invention are not necessarily so limited, andthat certain aspects of the embodiments may be applicable to larger, andpossibly smaller size scales.

In one aspect, embodiments of the invention describe a manner for masstransfer of an array of pre-fabricated micro devices with an array oftransfer heads. For example, the pre-fabricated micro devices may have aspecific functionality such as, but not limited to, a LED forlight-emission, silicon IC for logic and memory, and gallium arsenide(GaAs) circuits for radio frequency (RF) communications. In someembodiments, arrays of micro LED devices which are poised for pick upare described as having a 10 μm by 10 μm pitch, or 5 μm by 5 μm pitch.At these densities a 6 inch substrate, for example, can accommodateapproximately 165 million micro LED devices with a 10 μm by 10 μm pitch,or approximately 660 million micro LED devices with a 5 μm by 5 μmpitch. A transfer tool including an array of transfer heads matching aninteger multiple of the pitch of the corresponding array of micro LEDdevices can be used to pick up and transfer the array of micro LEDdevices to a receiving substrate. In this manner, it is possible tointegrate and assemble micro LED devices into heterogeneously integratedsystems, including substrates of any size ranging from micro displays tolarge area displays, and at high transfer rates. For example, a 1 cm by1 cm array of micro device transfer heads can pick up and transfer morethan 100,000 micro devices, with larger arrays of micro device transferheads being capable of transferring more micro devices.

In another aspect, embodiments of the invention describe a method andstructure for receiving a micro device or an array of micro devices on areceiving substrate. In an embodiment, a micro device or array of microdevices is transferred from a carrier substrate to a receiving substratewith a transfer head, or an array of transfer heads, which may beoperated in accordance with electrostatic principles. Without beinglimited to a particular theory, embodiments of the invention utilizetransfer heads and head arrays which operate in accordance withprinciples of electrostatic grippers, using the attraction of oppositecharges to pick up micro devices. In accordance with embodiments of thepresent invention, a pull-in voltage is applied to a transfer head inorder to generate a grip pressure on a micro device and pick up themicro device. In an embodiment, a grip pressure of greater than 1atmosphere is generated. For example, each transfer head may generate agrip pressure of 2 atmospheres or greater, or even 20 atmospheres orgreater without shorting due to dielectric breakdown of the transferheads.

In one embodiment, placing the micro device or array of micro devices onthe receiving substrate is performed with a punch-through technique inwhich the micro devices are placed on the receiving substrate bypunching through a B-staged thermoset passivation layer. A final curingoperation is then performed which may be associated with some amount ofshrinking of the thermoset passivation layer that further retains thetransferred array of micro devices on the receiving substrate duringsubsequent handling and processing operations. The term B-staged isknown in the art and refers to an intermediate stage in a thermosettingmaterial in which the material initially softens when heated but may notentirely fuse or dissolve. A B-staged material will cure upon continuedheating. The term A-staged is also known in the art and refers to anearly stage in a thermosetting material in which the material is fusibleand still soluble in certain liquids.

In one embodiment, placing the micro device or array of micro devices onthe receiving substrate is performed with a punch-through technique inwhich the micro devices are placed on the receiving substrate bypunching through a thermoplastic passivation layer heated above theglass transition temperature (Tg) of the thermoplastic duringpunch-through. In an embodiment, the thermoplastic passivation layer isheated above the Tg and below the melting temperature (Tm) of thethermoplastic during punch-through. Following punch-through, thethermoplastic passivation layer is cooled, and may further retain thetransferred array of micro devices on the receiving substrate duringsubsequent handling and processing operations.

Furthermore, where an active surface exists on a micro device, thepassivation layer (thermoset or thermoplastic) can passivate the activesurface. For example, where the micro device is a micro LED device, aquantum well layer may be exposed or contained near side surfaces of themicro LED device. In this manner, the passivation layer may laterallysurround and insulate the quantum well layer as result of thepunch-through operation.

In another aspect, embodiments of the invention describe a manner ofcombing the performance, efficiency, and reliability of wafer basedelectronics with the high yield, low cost, and mixed materials of thinfilm electronics to provide cost effect, energy efficient, highperformance devices. In accordance with embodiments of the invention,micro arrays of semiconductor LED devices fabricated in accordance withwafer based processing can be transferred to existing and new thin filmsubstrate technologies. Due to the small micro size and high efficiencyof the micro LED devices significant power savings of 20 times or morecan be realized compared to existing technologies. In an embodiment, amicro LED device is transferred to an active or passive matrix organicLED (OLED) backplane rather than forming a typical organic lightemitting layer. In this manner, a finished display device can befabricated that exhibits significant power savings, increased batterylife, and reduced peak pixel current compared to traditional OLEDdisplay technologies.

FIG. 1A is a cross-sectional side view illustration of a receivingsubstrate in accordance with an embodiment of the invention. Asillustrated, a first conductive layer 102 is formed on a substrate 100.An electrode line 106 may also be optionally formed on substrate 100.Substrate 100 may be a variety of substrates such as, but not limitedto, a display substrate, a lighting substrate, a substrate withfunctional devices such as transistors or integrated circuits (ICs), ora substrate with metal redistribution lines. Depending upon theparticular application, substrate 100 may be opaque, transparent, orsemi-transparent to the visible wavelength (e.g. 380-750 nm wavelength),and substrate 100 may be rigid or flexible. For example, substrate 100may be formed of glass or a polymer such as polyethylene terephthalate(PET), polyethelyne naphthalate (PEN), polycarbonate (PC),polyethersulphone (PES), aromatic fluorine-containing polyarylates(PAR), polycyclic olefin (PCO), and polyimide (PI). Depending upon theparticular application, either or both of conductive layer 102 andelectrode line 106 may be opaque, transparent, or semi-transparent tothe visible wavelength. Exemplary transparent conductive materialsinclude amorphous silicon, transparent conductive oxides (TCO) such asindium-tin-oxide (ITO) and indium-zinc-oxide (IZO), carbon nanotubefilm, or a transparent conducting polymer such aspoly(3,4-ethylenedioxythiophene) (PEDOT), polyaniline, polyacetylene,polypyrrole, and polythiophene. In an embodiment conductive layer 102 isapproximately 100 nm-200 nm thick ITO. In an embodiment, the conductivelayer 102 includes nanoparticles such as silver, gold, aluminum,molybdenum, titanium, tungsten, ITO, and IZO. The conductive layer 102or electrode line 106 may also be reflective to the visible wavelength.In an embodiment, a conductive layer 102 or electrode line 106 comprisesa reflective metallic film such as aluminum, molybdenum, titanium,titanium-tungsten, silver, or gold, or alloys thereof.

In an embodiment, conductive layer 102 functions as an electrode orelectrode line. In an embodiment, conductive layer 102 functions as ananode or anode line in the completed device, and electrode line 106functions as a cathode line in the completed device. It is to beappreciated that conductive layer 102 are electrode line 106 aredescribed as being related to the anode and cathode, respectively, inthe following description, however, the application can be reversed inother embodiments with conductive layer 102 and electrode line 106 beingrelated to the cathode and anode, respectively.

A bonding layer 104 may optionally be formed over the conductive layer102 to facilitate bonding of the micro device as described in furtherdetail below. In an embodiment, bonding layer 104 includes a materialsuch as indium, gold, silver, molybdenum, tin, aluminum, silicon, or analloy thereof and is approximately 0.1 μm to 0.5 μm thick. An electrodeline 106 may also be optionally formed on substrate 100. The electrodeline 106 may be formed of the same or different material from conductivelayer 102. In an embodiment, electrode line 106 is a cathode line outthe completed device.

FIG. 1B is a cross-sectional side view illustration of a receivingsubstrate in accordance with an embodiment of the invention. In theparticular embodiment illustrated, the receiving substrate 100 may be anactive matrix organic LED (AMOLED) backplane prior to the formation ofthe light emitting organic layer. For example, the AMOLED backplane caninclude a working circuitry 110, such as a traditional 2T1C (twotransistors, one capacitor) circuitry including a switching transistor,a driving transistor, and a storage capacitor. It is to be appreciatedthat the 2T1C circuitry is meant to be exemplary, and that other typesof circuitry or modifications of the traditional 2T1C circuitry arecontemplated in accordance with embodiments of the invention. Forexample, more complicated circuits can be used to compensate for currentdistribution to the driver transistor and the micro device, or for theirinstabilities. A passivation layer 108 may optionally be formed on thesubstrate 100 between the conductive layer 102 (e.g. anode) andelectrode line out 106 (e.g. cathode line out). Passivation layer 108may be formed of a variety of materials such as, but not limited to,silicon oxide (SiO₂), silicon nitride (SiN_(x)), poly(methylmethacrylate) (PMMA), benzocyclobutene (BCB), polyimide, and polyester.

It is to be appreciated that embodiments of the invention are compatiblewith a number of different substrates, and that the substrates describedwith regard to FIGS. 1A-1B are meant to be exemplary and not limiting.In interest of conciseness and to not obscure embodiments of theinvention, the following description is made with reference to theembodiment of the substrate illustrated in FIG. 1.

FIG. 2 is a cross-sectional side view illustration of a patternedpassivation layer 112 on a receiving substrate 100 in accordance with anembodiment of the invention. In the particular embodiment illustrated,the patterned passivation layer 112 is patterned to expose the electrodeline 106 (e.g. a cathode line out).

In an embodiment, the patterned passivation layer 112 is a B-stagedthermoset. The B-staged thermoset passivation layer 112 may be formed bydirectly applying the B-staged thermoset passivation layer, or by firstapplying an A-staged thermoset passivation layer on the receivingsubstrate 100 and covering the conductive layer 102, and optionallyelectrode line 106, followed by driving off the solvents and partiallycuring the A-staged thermoset passivation layer to form the B-stagedthermoset passivation layer. The A-staged or B-staged thermosetpassivation layer may be formed by a variety of techniques includingspin coating, screen printing, ink jet printing, dispensing, and spraycoating, and may be formed of a variety of materials including, but notlimited to benzocyclobutene (BCB) and epoxy. The rheology of theB-staged thermoset layer can be controlled by the amount ofcross-linking in the B-staged thermoset to allow for punch-through ofthe micro device without excessive flow. An opening exposing theelectrode line 106 may be formed during the A-stage application orB-stage application, such as with a screen printing or ink jet printingapplication, or alternatively when B-staged, where the opening may beformed by laser scribing or lithography. In an embodiment, a B-stagedthermoset passivation layer is formed on the receiving substrate 100with vacuum lamination.

In an embodiment, the patterned passivation layer 112 is athermoplastic. The thermoplastic passivation layer 112 may be formed bya variety of techniques including spin coating, screen printing, ink jetprinting, dispensing, and spray coating, and may be formed of a varietyof materials in which the rheology of the thermoplastic between the Tgand Tm of the thermoplastic is sufficient to allow for punch-through ofthe micro device without excessive flow. An opening exposing theelectrode line 106 may be formed during application of the patternedthermoplastic passivation layer, such as with a screen printing or inkjet printing application, or alternatively after application, where theopening may be formed by laser scribing or lithography. In anembodiment, a thermoplastic passivation layer is formed on the receivingsubstrate 100 with vacuum lamination.

FIGS. 3A-3C are cross-sectional side view illustrations of an array oftransfer heads picking up an array of micro devices from a carriersubstrate in accordance with an embodiment of the invention. Referringto FIG. 3A, an array of transfer heads 302 supported by a transfer headsubstrate 300 are positioned over an array of micro devices 400supported on a carrier substrate 200. A heater 306 and heat distributionplate 304 may optionally be attached to the transfer head substrate 300.A heater 204 and heat distribution plate 202 may optionally be attachedto the carrier substrate 200. The array of micro devices 400 arecontacted with the array of transfer heads 302, as illustrated in FIG.3B, and picked up from the carrier substrate 200 as illustrated in FIG.3C.

In an embodiment, the array of micro devices 400 are picked up with anarray of transfer heads 302 operating in accordance with electrostaticprinciples. In an embodiment, a bonding layer (illustrated in furtherdetail in FIG. 3A) may be formed between the array of micro devices 400and the carrier substrate 200. In such an embodiment, heat may beapplied to the bonding layer from either or both heaters 204, 306 priorto or during pick up to create a phase change in the bonding layer. Forexample, the bonding layer may be heated above a liquidus temperature ofthe bonding layer to create a phase change from solid to liquid state.In an embodiment, the bonding layer has a liquidus temperature of 350°C. or below, or more specifically 200° C. or below.

FIG. 3D is a cross-sectional side view illustration of a transfer head302 holding a micro LED device 400 over a receiving substrate 100 with apatterned passivation layer 112 in accordance with an embodiment of theinvention. In the embodiment illustrated, the transfer head 302 issupported by a transfer head substrate 300. As described above, a heater306 and heat distribution plate 304 may optionally be attached to thetransfer head substrate to apply heat to the transfer head 302. A heater152 and heat distribution plate 150 may also, or alternatively,optionally be used to transfer heat to the conductive layer 102 andoptional bonding layer 104 on the receiving substrate 100 and/oroptional bonding layer 410 on a micro device 400 described below.

Still referring to FIG. 3D, a close-up view of an exemplary micro LEDdevice 400 is illustrated in accordance with an embodiment. It is to beappreciated, that the specific micro LED device 400 illustrated isexemplary and that embodiments of the invention are not limited. Forexample, embodiments of the invention may also be applicable to othermicro LED devices such as, but not limited to, the micro LED devices inU.S. patent application Ser. No. 13/372,222, U.S. patent applicationSer. No. 13/436,260, and U.S. patent application Ser. No. 13/458,932,all of which are incorporated herein by reference. Embodiments of theinvention may also be applicable to other micro devices including, butnot limited to, other micro semiconductor devices which are designed insuch a way so as to perform in a controlled fashion a predeterminedelectronic function (e.g. diode, transistor, integrated circuit) orphotonic function (LED, laser).

In the particular embodiment illustrated, the micro LED device 400includes a micro p-n diode 450 and a metallization stack 420. A bondinglayer 410 may optionally be formed below the metallization stack 420,with the metallization stack 420 between the micro p-n diode 450 and thebonding layer 410. In an embodiment, the micro p-n diode 450 includes atop n-doped layer 414, one or more quantum well layers 416, and a lowerp-doped layer 418. The micro p-n diodes can be fabricated with straightsidewalls or tapered sidewalls. In certain embodiments, the micro p-ndiodes 450 possess outwardly tapered sidewalls 453 (from top to bottom).In certain embodiments, the micro p-n diodes 450 possess inwardlytapered sidewall (from top to bottom). The metallization stack 420 mayinclude one or more layers. For example, the metallization stack 420 mayinclude an electrode layer and a barrier layer between the electrodelayer and the optional bonding layer. The metallization stack 420 may betransparent to the visible wavelength range (e.g. 380 nm-750 nm) oropaque. The metallization stack 420 may optionally include a reflectivelayer, such as a silver layer. The micro p-n diode and metallizationstack may each have a top surface, a bottom surface and sidewalls. In anembodiment, the bottom surface 451 of the micro p-n diode 450 is widerthan the top surface 452 of the micro p-n diode, and the sidewalls 453are tapered outwardly from top to bottom. The top surface of the microp-n diode 450 may be wider than the bottom surface of the p-n diode, orapproximately the same width. In an embodiment, the bottom surface 451of the micro p-n diode 450 is wider than the top surface of themetallization stack 420. The bottom surface of the micro p-n diode mayalso be approximately the same width as the top surface of themetallization stack.

A conformal dielectric barrier layer 460 may optionally be formed overthe micro p-n diode 450 and other exposed surfaces. The conformaldielectric barrier layer 460 may be thinner than the micro p-n diode450, metallization stack 420 and the optional bonding layer 410 so thatthe conformal dielectric barrier layer 260 forms an outline of thetopography it is formed on. In an embodiment, the micro p-n diode 450 isseveral microns thick, such as 3 μm or 5 μm, the metallization stack 420is 0.1 μm-2 μm thick, and the optional bonding layer 410 is 0.1 μm-1 μmthick. In an embodiment, the conformal dielectric barrier layer 460 isapproximately 50-600 angstroms thick aluminum oxide (Al₂O₃). Theconformal dielectric barrier layer 460 may protect against charge arcingbetween adjacent micro p-n diodes during the pick up process, andthereby protect against adjacent micro p-n diodes from sticking togetherduring the pick up process. The conformal dielectric barrier layer 460may also protect the sidewalls 453, quantum well layer 416 and bottomsurface 451, of the micro p-n diodes from contamination which couldaffect the integrity of the micro p-n diodes. For example, the conformaldielectric barrier layer 460 can function as a physical barrier towicking of the bonding layer material 410 up the sidewalls and quantumlayer 416 of the micro p-n diodes 450. The conformal dielectric barrierlayer 260 may also insulate the micro p-n diodes 450 once placed on thereceiving substrate. In an embodiment, the conformal dielectric barrierlayer 460 span sidewalls 453 of the micro p-n diode, and may cover thequantum well layer 416 in the micro p-n diode. The conformal dielectricbarrier layer may also partially span the bottom surface 451 of themicro p-n diode, as well as span sidewalls of the metallization stack420. In some embodiments, the conformal dielectric barrier layer alsospans sidewalls of a patterned bonding layer 410. A contact opening maybe formed in the conformal dielectric barrier layer 460 exposing the topsurface 452 of the micro p-n diode. The contact opening 462 may have asmaller width than the top surface 452 of the micro p-n diode and theconformal dielectric barrier layer 460 forms a lip around the edges ofthe top surface 452 of the micro p-n diode. Alternatively the contactopening 462 may have a slightly larger width than the top surface of themicro p-n diode or approximately the same width as the top surface ofthe micro p-n diode. In an embodiment, a conformal dielectric barrierlayer 260 is not present, and the passivation layer 112 is used toinsulate the micro p-n diodes 450 once placed on the receivingsubstrate.

FIG. 3E is a cross-sectional side view illustration of an array oftransfer heads holding an array micro LED devices 400 over a receivingsubstrate with a patterned passivation layer 112 in accordance with anembodiment of the invention. FIG. 3E is substantially similar to thestructure illustrated in FIG. 3D with the primary difference being theillustration of the transfer of an array of micro devices as opposed toa single micro device within the array of micro devices.

FIG. 4A is a cross-sectional side view illustration of a micro LEDdevice punched through a passivation layer on a receiving substrate inaccordance with an embodiment of the invention. Punch-through may beaccomplished by physically driving the micro LED device 400 through thepassivation layer 112 with the transfer head 302 until contacting theconductive layer 102 or optional bonding layer 104 on the receivingsubstrate 100. As illustrated, the micro LED device 400 may bepunched-through the passivation layer 112 so that passivation layer 112laterally surrounds the quantum well layer 416. The passivation layer112 may also be thinner than the height of the micro LED device 400 sothat electrical contact can be made with the top surface 452 of themicro LED device.

Punch-through may also be aided by the application of heat through thetransfer head 302 or receiving substrate 100. In an embodiment where thepassivation layer 112 is a UV curable or thermally curable B-stagedthermoset, the application of heat can melt or soften the B-stagedthermoset passivation layer 112 to aid in the punch-through. Thus, theamount of applied pressure, heat, and amount of cross-linking in theB-staged thermoset can be controlled to achieve punch-though.Application of UV energy after punch-through can then be used to curethe thermoset passivation layer 112 where the thermoset passivationlayer 112 is UV curable. In an embodiment where the passivation layer122 is a thermally curable B-staged thermoset, continued application ofheat after punch-through can then be used to cure the thermosetpassivation layer 112. In an embodiment, where the passivation layer 112is a thermoplastic material the thermoplastic passivation layer 112 isheated above the Tg, and more specifically, above the Tg and below theTm of the thermoplastic material during punch-through. Thus, the amountof pressure and heat applied to the thermoplastic material can becontrolled to achieve punch-though.

In certain embodiments, the application of heat during punch-through canalso result in reflowing of one or both of the optional bonding layers410, 104 or diffusion between layers to assist with bonding. Inaddition, reflowing of any of the bonding layers 410, 104 can result informing a new bonding layer with a higher melting temperature. In oneembodiment, the application of heat not only aids with punch-through oflayer 112, the application of heat also causes at least partial reflowand solidification of the bonding layers(s) 410, 104. For example, theapplication of heat can lead to the formation of an alloy having ahigher Tm than that of the reflowed or diffused layer(s).

In an embodiment, the punch-through and release of the micro devices onthe receiving substrate is performed in ten seconds or less, or moreparticularly one second or less. Where heat is applied, it is possibleto rapidly reflow either of the optional bonding layer(s) 410, 104 toassist in bonding and to soften or initially melt the passivation layer112, which can be a thermal or UV curable B-staged thermoset, or athermoplastic. Following the release of the array of micro devices fromthe array of transfer heads, the passivation layer 112 is hardened tosecure the array of micro devices on the receiving substrate. Where thepassivation layer 112 is a thermoplastic, hardening is effected byallowing the thermoplastic material to cool. Where the passivation layer112 is a B-staged thermoset, the passivation layer can be final curedthrough the application of UV energy or heat for an order of minutes orhours to effect curing. In an embodiment, heat can be applied from belowthe receiving substrate 100 with heater 152 and/or heat distributionplate 150. Heat can also be applied from above the receiving substrate100. UV energy can also be applied from above or below the receivingsubstrate. In an embodiment, the receiving substrate is transferred to acuring chamber to effect curing following the release of the array ofmicro devices.

FIG. 4B is a cross-sectional side view illustration of an array of microLED devices punched through a passivation layer on a receiving substratein accordance with an embodiment of the invention. FIG. 4B issubstantially similar to the structure illustrated in FIG. 4A with theprimary difference being the illustration of the transfer of an array ofmicro devices as opposed to a single micro device within the array ofmicro devices.

Referring now to FIG. 5, following hardening of the punched-throughpassivation layer 112 a second conductive layer 114 and optional barrierlayer 116 may be formed over the micro LED device 400 and receivingsubstrate 100 in accordance with an embodiment of the invention. In anembodiment, the second conductive layer 114 is a transparent materialsuch as amorphous silicon, transparent conductive oxides (TCO) such asindium-tin-oxide (no) and indium-zinc-oxide (IZO), carbon nanotube film,or a transparent conducting polymer such aspoly(3,4-ethylenedioxythiophene) (PEDOT), polyaniline, polyacetylene,polypyrrole, and polythiophene. In an embodiment, the second conductivelayer 114 includes nanoparticles such as silver, gold, aluminum,molybdenum, titanium, tungsten, ITO, and indium-zinc-oxide (IZO). Thesecond conductive layer 114 may also be reflective to the visiblewavelength. In an embodiment, a reflective conductive layer 114comprises a metallic film such as aluminum, molybdenum, titanium,titanium-tungsten, silver, or gold, or alloys thereof. In an embodiment,an optional barrier layer 116 is formed over the second conductive layer114. For example, the optional barrier layer 116 can act as a barrier tooxygen or moisture absorption by any underlying layers during subsequentprocessing. In an embodiment, barrier layer 116 is formed from aninorganic material (e.g. SiO_(x)N_(y), SiN_(x), Al₂O₃, etc.) for oxygenand moisture protection. Barrier layer 116 may also be transparent oropaque to the visible wavelength, and may be rigid or flexible. In anembodiment, the barrier layer 116 is Al₂O₃, and may be deposited by avariety of methods including atomic layer deposition (ALD).

Referring now to FIG. 6 and FIG. 7, alternative embodiments areillustrated for forming an electrode line 118 (e.g. a cathode line out)where one is not already formed. Similar to electrode line 106, theelectrode line 118 may function may be associated with an anode orcathode. In an embodiment, electrode line 118 is a cathode line out.Electrode line 118 may be formed of any of the materials alreadydescribed with regard to layers 102, 106, and 114. FIG. 6 is anillustration of an embodiment in which an electrode line 118 is formedon conductive layer 114 directly over the micro LED device 400. Inanother embodiment electrode line 118 is formed directly on the microLED device 400. FIG. 7 is an illustration of an embodiment in whichelectrode line 118 is formed on a trace portion of second conductivelayer 114. In both embodiments, an opening may be formed in the optionalbarrier layer 116, if present, in order to expose the second conductivelayer 114 prior to formation of the electrode line 118.

FIG. 8 is a cross-sectional side view illustration of cover layer 120formed over the exemplary structure of FIG. 5 in accordance with anembodiment. In the particular embodiment illustrated the cover layer 120is conformal to the topography of the micro LED device 400 and overallstructure over substrate 100. Cover layer 120 may function to provideboth chemical passivation and physical protection to the underlyingstructure. Cover layer 120 may also be flexible, and may be transparent.Cover layer 120 may be formed of a variety of materials such as, but notlimited to, silicon oxide (SiO₂), silicon nitride (SiN_(x)), poly(methylmethacrylate) (PMMA), benzocyclobutene (BCB), polyimide, and polyester.

As described up to this point, the layers on which the micro LED device400 are supported and covered by can be transparent or opaque to thevisible wavelength. Accordingly, the structure illustrated in FIG. 8 canemit light through either the top cover 120, through the bottomsubstrate 100, or both depending on the selection of materials and typeof substrate.

FIG. 9 is a cross-sectional side view illustration an embodiment inwhich a reflective layer 122 is formed over the micro LED device 400prior to formation of the top cover 120 to produce a bottom emittingstructure. For example, reflective layer 122 can be evaporated orsputtered metallic material such as aluminum. In this manner, lightemitting upward from the micro LED device 400 is reflected back throughthe bottom substrate 100. In such an embodiment, the metallic stack 420and/or optional bonding layers 410/104 may be substantially transparentto the visible wavelength. Transparency can be controlled by theselection of materials and/or thickness of the layers.

FIG. 10 is a cross-sectional side view illustration of an embodiment inwhich a black matrix layer 124 is formed around a micro LED device priorto formation of the top cover 120 in order to block light emission, andto separate light emission from the micro LED device 400 from one ormore adjacent micro LED devices 400. In such an embodiment, thestructure illustrated in FIG. 10 can emit light through either the topcover 120, through the bottom substrate 100, or both depending on theselection of materials and type of substrate. Black matrix 124 can beformed form a method that is appropriate based upon the material used.For example, black matrix 124 can be applied using ink jet printing,sputter and etching, spin coating with lift-off, or a printing method.Exemplary black matrix materials include carbon, metal films (e.g.nickel, aluminum, molybdenum, and alloys thereof), metal oxide films(e.g. chromium oxide), and metal nitride films (e.g. chromium nitride),organic resins, glass pastes, and resins or pastes including a blackpigment or silver particles.

While cover 120 has been described as being conformal to the topographyof the underlying structure, a separate cover plate can also be securedto the structure in combination with cover 120, or in the alternative tocover 120 in accordance with embodiments of the invention. FIGS. 11-12are cross-sectional side view illustrations of attaching a cover plate126 over a micro LED device 400 on a receiving substrate 100 inaccordance with an embodiment of the invention. As illustrated, coverplate 126 can be attached to the substrate 100 with an adhesive 128 andmay surround a plurality of pixels on the substrate 100. For example,adhesive 128 can be, but is not limited to, a frit glass seal or epoxyformed along the edge of the cover with a dispenser or screen printing.Cover 126 can be provided in place of or in combination with cover 120.In an embodiment, cover plate 126 is transparent glass or plastic.

FIGS. 13-14A are cross-sectional side view illustrations of attaching acover plate 126 over a micro LED device 400 on a receiving substrate 100in accordance with an embodiment of the invention. FIGS. 13-14A aresimilar to FIGS. 11-12 with one difference being that a black matrix 124is attached to the cover plate 126 prior to attaching the cover plate126 to the substrate 100. FIG. 14B is a cross-sectional side viewillustration of a cover plate 126 and black matrix 124 over an array ofmicro LED devices 400 on a receiving substrate in accordance with anembodiment of the invention. As illustrated, cover plate 126 is attachedto the substrate 100 with an adhesive 128 surrounding a plurality ofpixels on the substrate. In the embodiment illustrated, the black matrix124 is patterned on the cover plate 126 and includes a plurality ofopenings corresponding to locations directly above the locations of themicro LED devices 400 on substrate 100.

FIGS. 15-17 are schematic illustrations of passive matrix displaylayouts in accordance with embodiments of the invention. As illustrated,a pixel can include an array of subpixels. In the particular embodimentsillustrated, each pixel comprises three subpixels, one with a redemitting LED device 400R, one with a blue emitting LED device 400B, andone with a green emitting LED device 400G. For example, a red emittingLED device 400R (e.g. 620-750 nm wavelength) can include a micro p-ndiode layer formed of a semiconductor material such as aluminum galliumarsenide (AlGaAs), gallium arsenide phosphide (GaAsP), aluminum galliumindium phosphide (AlGaInP), and gallium phosphide (GaP). For example, agreen emitting LED device 400G (e.g. 495-570 nm wavelength) can includea micro p-n diode layer formed of a semiconductor material such asindium gallium nitride (InGaN), gallium nitride (GaN), gallium phosphide(GaP), aluminum gallium indium phosphide (AlGaInP), and aluminum galliumphosphide (AlGaP). For example, a blue emitting LED device 400B (e.g.450-495 nm wavelength) can include a micro p-n diode layer formed of asemiconductor material such as gallium nitride (GaN), indium galliumnitride (InGaN), and zinc selenide (ZnSe).

While the following pixel and subpixel arrangements are described withregard to a red-green-blue (RGB) subpixel arrangement, it is to beappreciated that the RGB arrangement is exemplary and that embodimentsare not so limited. Other subpixel arrangements such as BGR orred-green-blue-yellow (RGBY), red-green-blue-yellow-cyan (RGBYC) can beutilized, as well subpixel rendering configurations in accordance withembodiments of the invention.

Referring now to FIG. 15, in the embodiment illustrated the LED devices400R, 400G, 400B are placed on the first conductive layer 102 (e.g.anode line out). The LED devices are connected to the electrode line106, 118 (e.g. cathode line out) by second conductive layer 114, forexample as described above with regard to FIG. 5 or FIG. 7. Referring toFIG. 16, in the embodiment illustrated the LED devices 400R, 400G, 400Bare placed on an electrode trace 103 connected with the first conductivelayer 102. Similar to FIG. 15, the LED devices are connected to theelectrode line 106, 118 by second conductive layer 114, for example asdescribed above with regard to FIG. 5 or FIG. 7. Referring to FIG. 17,in the embodiment illustrated, the LED devices 400R, 400G, 400B areplaced on the first conductive layer 102, and the electrode line 118 isformed over the LED devices, for example as described above with regardto FIG. 6.

A circuit diagram of a passive matrix display 1800 for any of thearrangements in FIGS. 15-17 is illustrated in FIG. 18 in accordance withan embodiment of the invention. As illustrated, the anode lines out 102are oriented horizontally, the cathode lines out 106, 118 are orientedvertically, and the LED devices are placed between the lines. Thecathode lines out 106, 118 function as data lines, and are driven by oneor more data drivers. The anode lines out 102 function as scan lines,and are driven by one or more scan drivers.

FIG. 19 is a schematic illustration of a subpixel in an active matrixdisplay in accordance with embodiments of the invention. Moreparticularly, FIG. 19 illustrates an embodiment of a micro LED device400 placed in an aperture 160 over the anode 102 (e.g. ITO layer) of anAMOLED backplane subpixel including working circuitry such as atraditional 2T1C (two transistors, one capacitor) circuitry including aswitching transistor T1, a driving transistor T2, and a storagecapacitor Cs. It is to be appreciated that the 2T1C circuitry is meantto be exemplary, and that other types of circuitry or modifications ofthe traditional 2T1C circuitry are contemplated in accordance withembodiments of the invention.

As illustrated, the micro LED device 400 may occupy less than theavailable space of the aperture 160 depending upon application. Table 1below includes calculations of diagonal pixel size based upon pixeldensity, along with minimum subpixel size estimation with an RGB pixellayout in accordance with embodiments of the invention. In theseexamples, minimum subpixel size is approximated as being one third ofthe diagonal pixel size. It is to be appreciated that this numberrepresents a minimum estimation, and is dependent upon the subpixelarrangement and landscape of the working circuitry.

TABLE 1 Pixel Density Diagonal Pixel Minimum Subpixel (per inch) Size(μm) Size (μm) 500 51 17 300 85 28 200 127 42 100 254 85

Where a display has a pixel density of 100 pixels per diagonal inch(e.g. a computer monitor), this corresponds to a diagonal pixel size of254 microns. With an RGB pixel layout, a subpixel illustrated in FIG. 19is estimated to have a diagonal size of at least 85 microns. Where thedisplay has a pixel density of 300 pixels per diagonal inch (e.g. amobile phone, tablet) this corresponds to a diagonal pixel size of 85microns. With an RGB pixel layout, a subpixel illustrated in FIG. 19 isestimated to have a diagonal size of at least 28 microns. Thus, as shownin Table 1 displays including substrates receiving micro LED devices inaccordance with embodiments of the invention may be scalable down topixel densities greater than the maximum resolution of a perfect humaneye, which is estimated as being somewhere between 300 and 500 pixelsper inch.

FIG. 20 is a circuit diagram of a subpixel with 2T1C circuitry in anactive matrix display in accordance with an embodiment of the invention.In such an embodiment, the circuit includes a switching transistor T1, adriving transistor T2, a storage capacitor Cs and a micro LED device400. The transistors T1, T2 can be any type of transistor such as a thinfilm transistor. For example, the switching transistor T1 can be an-type metal-oxide semiconductor (NMOS) transistor, and the drivingtransistor T2 can be a p-type metal-oxide semiconductor (PMOS)transistor. The switching transistor T1 has a gate electrode connectedto a scan line V_(select) and a first source/drain electrode connectedto a data line V_(data). The driving transistor T2 has a gate electrodeconnected to a second source/drain electrode of the switching transistorT1 and a first source/drain electrode connected to a power sourceV_(dd). The storage capacitor Cs is connected between the gate electrodeof the driving transistor T2 and the first source/drain electrode of thedriving transistor T2. The micro LED device 400 has an anode electrodeconnected to a second source/drain electrode of the driving transistorT2 and a cathode electrode connected to a ground V_(ss).

In operation, a voltage level scan signal turns on the switchingtransistor T1, which enables the data signal to charge the storagecapacitor Cs. The voltage potential that stores within the storagecapacitor Cs determines the magnitude of the current flowing through thedriving transistor T2, so that the micro LED device 400 can emit lightbased on the current. It is to be appreciated that the 2T1C circuitry ismeant to be exemplary, and that other types of circuitry ormodifications of the traditional 2T1C circuitry are contemplated inaccordance with embodiments of the invention. For example, morecomplicated circuits can be used to compensate for current distributionto the driver transistor and the micro device, or for theirinstabilities.

FIG. 21 is a circuit diagram of a pixel in an active matrix display 2100in accordance with an embodiment of the invention. As illustrated, thescan lines V_(select) are oriented horizontally and a driven by one ormore scan drivers, and data lines V_(data) are oriented vertically andare driven by one or more data drivers. The red, green, and blue lightemitting micro LED devices are placed between the scan lines and datalines.

FIG. 22 illustrates a display system 2200 in accordance with anembodiment. The display system houses a processor 2210, data receiver2220, a display 2230, and one or more display driver ICs 2240, which maybe scan driver ICs and data driver ICs. The data receiver 2220 may beconfigured to receive data wirelessly or wired. Wireless may beimplemented in any of a number of wireless standards or protocolsincluding, but not limited to, Wi-Fi (IEEE 802.11 family), WiMAX (IEEE802.16 family), IEEE 802.20, long term evolution (LTE), Ev-DO, HSPA+,HSDPA+, HSUPA+, EDGE, GSM, GPRS, CDMA, TDMA, DECT, Bluetooth,derivatives thereof, as well as any other wireless protocols that aredesignated as 3G, 4G, 5G, and beyond. The one or more display driver ICs2240 may be physically and electrically coupled to the display 2230.

In some embodiments, the display 2230 includes one or more micro LEDdevices 400 that are formed in accordance with embodiments of theinvention described above. For example, the display 2230 may includepixels or subpixels in which a micro LED device 400 is received bypassivation layer 112 laterally surrounding the quantum well layer ofthe micro LED device.

Depending on its applications, the display system 2200 may include othercomponents. These other components include, but are not limited to,memory, a touch-screen controller, and a battery. In variousimplementations, the display system 2200 may be a television, tablet,phone, laptop, computer monitor, kiosk, digital camera, handheld gameconsole, media display, ebook display, or large area signage display.

In utilizing the various aspects of this invention, it would becomeapparent to one skilled in the art that combinations or variations ofthe above embodiments are possible for receiving a micro device.Although the present invention has been described in language specificto structural features and/or methodological acts, it is to beunderstood that the invention defined in the appended claims is notnecessarily limited to the specific features or acts described. Thespecific features and acts disclosed are instead to be understood asparticularly graceful implementations of the claimed invention usefulfor illustrating the present invention.

What is claimed is:
 1. A display comprising: a display substrate; anarray of bottom conductive layers on the display substrate; an electrodeline on the substrate; a first passivation layer spanning across thedisplay substrate and directly over the array of bottom conductivelayers; a corresponding array of integrated circuit (IC) devices bondedto the array of bottom conductive layers, and embedded within the firstpassivation layer; wherein the first passivation layer laterallysurrounds each IC device; and a transparent top conductive layerspanning directly over the first passivation layer and the array of ICdevices and in electrical contact with the electrode line.
 2. Thedisplay of claim 1, further comprising a second passivation layer overthe display substrate and underneath the first passivation layer,wherein the second passivation layer includes an array of openingsexposing the array of bottom conductive layers.
 3. The display of claim1, further comprising a display driver IC coupled to the displaysubstrate.
 4. The display of claim 3, wherein the display driver IC is ascan driver IC.
 5. The display of claim 4, wherein the array of bottomconductive layers is coupled to the scan driver IC.
 6. The display ofclaim 3, wherein the display driver IC is a data driver IC.
 7. Thedisplay of claim 6, wherein the electrode line is coupled to the datadriver IC.
 8. The display of claim 1, wherein the array of IC devices isbonded to the array of bottom conductive layers with a correspondingarray of bonding layers.
 9. The display of claim 8, wherein each bondinglayer in the array of bonding layers is an alloy bonding layer.
 10. Thedisplay of claim 1, further comprising a black matrix layer over thetransparent top conductive layer.
 11. The display of claim 10, furthercomprising a barrier layer between the black matrix layer and thetransparent top conductive layer.
 12. The display of claim 10, furthercomprising a cover layer over the black matrix layer.
 13. The display ofclaim 1, further comprising an opening in the first passivation layerover the electrode line, wherein the transparent top conductive layerspans within the opening to contact the electrode line.
 14. The displayof claim 13, wherein the first passivation layer is a thermosetmaterial.
 15. The display of claim 14, wherein the first passivation istransparent.
 16. The display of claim 14, further comprising a secondpassivation layer over the display substrate and underneath the firstpassivation layer, wherein the second passivation layer includes anarray of openings exposing the array of bottom conductive layers,wherein the second passivation layer is a thermoset material.